<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
<head>
<!-- Copyright 1997 The Open Group, All Rights Reserved -->
<title>realloc</title>
</head><body bgcolor=white>
<center>
<font size=2>
The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

</font></center><hr size=2 noshade>
<h4><a name = "tag_000_007_1927">&nbsp;</a>NAME</h4><blockquote>
realloc - memory reallocator
</blockquote><h4><a name = "tag_000_007_1928">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="stdlib.h.html">stdlib.h</a>&gt;

void *realloc(void *<i>ptr</i>, size_t <i>size</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_007_1929">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>realloc()</i>
function changes the size of the memory object pointed to by
<i>ptr</i>
to the size specified by
<i>size</i>.
The contents of the object will remain unchanged up to the lesser of the
new and old sizes.
If the new size of the memory object would require
movement of the object, the space for the previous instantiation of the
object is freed.
If the new size is larger, the contents of the newly allocated portion of
the object are unspecified.  If
<i>size</i>
is 0 and
<i>ptr</i>
is not a null pointer,
the object pointed to is freed.
If the space cannot be allocated, the
object remains unchanged.
<p>
If
<i>ptr</i>
is a null pointer,
<i>realloc()</i>
behaves like
<i><a href="malloc.html">malloc()</a></i>
for the specified size.
<p>
If
<i>ptr</i>
does not match a pointer returned earlier by
<i><a href="calloc.html">calloc()</a></i>,
<i><a href="malloc.html">malloc()</a></i>
or
<i>realloc()</i>
or if the space has previously been deallocated by a call to
<i><a href="free.html">free()</a></i>
or
<i>realloc()</i>,
the behaviour is undefined.
<p>
The order and contiguity of storage allocated by successive calls to
<i>realloc()</i>
is unspecified.
The pointer returned if the allocation succeeds is suitably
aligned so that it may be assigned to a pointer to any type of
object and then used to access such an object in the space
allocated (until the space is explicitly freed or reallocated).
Each such allocation will yield a pointer to an object disjoint
from any other object.
The pointer returned points to the start (lowest byte address) of
the allocated space.
If the space cannot be allocated, a null pointer is returned.
</blockquote><h4><a name = "tag_000_007_1930">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion with a size not equal to 0,
<i>realloc()</i>
returns a pointer to the (possibly moved) allocated space.
If
<i>size</i>
is 0, either a null pointer or a unique pointer that
can be successfully passed to
<i><a href="free.html">free()</a></i>
is returned.
If there is
not enough available memory,
<i>realloc()</i>
returns
a null pointer
&nbsp;and sets
<i>errno</i>
to [ENOMEM].
</blockquote><h4><a name = "tag_000_007_1931">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>realloc()</i>
function will fail if:
<dl compact>

<dt>[ENOMEM]<dd>
Insufficient memory is available.

</dl>
</blockquote><h4><a name = "tag_000_007_1932">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_1933">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_1934">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_1935">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="calloc.html">calloc()</a></i>,
<i><a href="free.html">free()</a></i>,
<i><a href="malloc.html">malloc()</a></i>,
<i><a href="stdlib.h.html">&lt;stdlib.h&gt;</a></i>.
</blockquote><h4>DERIVATION</h4><blockquote>
Derived from Issue 1 of the SVID.
</blockquote><hr size=2 noshade>
<center><font size=2>
UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]

</font></center><hr size=2 noshade>
</body></html>

